User blog comment:QueenCupcake025/MY GARDEVOIR AND GALLADE DON'T GET ALONG WELL!!/@comment-32391784-20170629192545

if they "don't get along well" there is a 20% chance of them laying an egg every roughly-250 steps. They will lay an egg eventually, it'll take longer than normal.

The only time they won't lay an egg is if the man says they prefer to play with other pokémon.